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Automated Screening of Pap Smears Improves Accuracy

Automated Screening of Pap Smears Improves Accuracy

November 01, 1998

Over the past several years, a number of biotechnology companies have
developed enhanced screening methods designed to improve Pap smear
accuracy. Until recently, however, these screening methods were used
only as quality control devices, ie, as a way for laboratories to
check their work. Since federal guidelines only require that 10% of
all slides be rescreened, there is still an opportunity for error.

In May 1998, the AutoPap Primary Screening System, manufactured by
NeoPath, became the first, and to date only, FDA-approved
computer-assisted primary Pap smear screening device for use in the
early detection of cervical cancer. Because this is a new technology,
a brief discussion about automated screening and how it works is
warranted before a discussion of how it might help reduce malpractice claims.

Computers are especially suited to Pap smear screening because,
unlike human beings, they do not suffer from stress or fatigue, which
can result in a missed reading. The AutoPap System uses high-speed
video microscopes (see figure) and
specialized visual intelligence software to render, analyze, and
classify slides in the order of probability that abnormal cells are
present. Once the system detects the slide, it reads the bar code and
touches the slide to understand the orientation of its surface. The
system scans the entire specimen at low power to build a 3D map of
the specimen.

Information from each scanned field is then sent to computers for
processing, and these images are run through a series of
interpretation algorithms to determine the final results. At
completion, cytotech-nologists receive a printout of the results and
remove those slides that require further review.

In premarket tests, a study of 25,000 Pap smears reviewed under
standard laboratory practice and with the AutoPap System found that
the computer system helped catch 33% more abnormal cells, including
two possible cancers that technicians missed.[1] The study also
showed a 16% improvement in the detection of false positives. (While
no medical malpractice claim has ever been filed due to a
false-positive result, a patient could theoretically claim emotional
distress and point to any unnecessary testing or procedure costs.)

Moreover, the AutoPap System uses two unique slide classification
algorithms to identify those Pap smears with the highest likelihood
of an abnormality. As an initial screener, the AutoPap System
identifies up to 25% of slides that receive AutoPap review only and
may be archived as normal. The remaining 75% are ranked in order of
highest probability of containing abnormal cells. This provides a
common benchmark from which cyto-technologists can make a more
accurate diagnosis, and allows them to spend more time reviewing
those slides that are most likely to contain abnormal cells.

As for errors due to insufficient sampling, the AutoPap System
automatically identifies and rejects unsatisfactory slides that need
to be returned to physicians, thus reducing the subjective dilemma of
whether to let an unsatisfactory slide go through the system.

It should also be noted that the AutoPap Primary Screening System is
not intended to replace laboratory slide review processes for
"high-risk" slides. High-risk slides are those for which a
health care provider has requested special handling because of a
specified concern (such as a prior abnormal gynecologic history;
previous diagnosis of HPV, dysplasia, or HIV infection; or post-menopausal
or vaginal bleeding) or those for which the clinical laboratory,
through its own procedures, has identified a need for a high-level screening.[2]

Will the Payers Pay?

While an increasing number of insurance companies are beginning to
take notice of this technology and raise reimbursement levels
accordingly, many are not yet funding enhanced Pap smear screening methods.

Thus, it can be argued that a physician who does not recommend the
use of automated screening has not violated the current standard of
care. However, physicians do not have the right to decide what the
patient can afford or is willing to pay. Increasing pressure from
womens health advocates, physician groups, and the biotech
industry for insurance providers to cover enhanced screening may soon
resolve this doctors dilemma.

In fact, Congress is currently debating legislation that would amend
the Social Security Act to increase the amount of payment under the
Medicare program for Pap smear screening effective January 1, 1999.[3]

Although this legislation does not specifically include coverage for
enhanced screening options, it might be an important first step in
opening the door to that possibility and could help establish a
precedent for private insurers to follow.

Alternative Methods

Another automated screening device, PapNet, manufactured by
Neuromedical Systems Inc, has been FDA approved only for use in
quality control. PapNet uses neural network technology to detect
suspicious-appearing cells and digitally enlarge the images of these
cells for focused review by cytologists.

While cost should not be the sole determining factor when
recommending an enhanced screening method, it should be noted that
laboratories generally charge patients an extra $30 to $40 per Pap
smear for rescreening with PapNet.[4] In contrast, most Pap smears
slides screened with the AutoPap System, either as a primary screen
or for quality control, cost an additional $8 to $12, depending on
the laboratory.[5]

The cost is lower partly because AutoPap-assisted screening can be
performed directly in the laboratory, while PapNet slides must be
sent back to the manufacturers facilities for review. Sending
the slide back to another lab may also jeopardize the integrity of
the sample.

Since the AutoPap Primary Screening System is a new technology, it is
not yet clear what role it may play in Pap smear litigation cases.
Yet, its ability to provide greater accuracy and increased capacity
will likely lead to increased use. As that transpires, the standard
of care may shift, leading to a change in jury decisions.

A physicians failure to recommend the use of an enhanced
screening method, in and of itself, probably will not result in a win
for the plaintiff, although it could be a factor in the overall
outcome of the claim. On the other hand, if the physician can show
that he or she ordered the most accurate and up-to-date screening
method for the patients Pap smear, it could increase the
chances of an outcome favorable to the defense.

With this in mind, the last article in this series (to appear next
month) will provide some recommendations for reducing the risk of a
malpractice claim regarding Pap smears.